Herdecke is a town in the district of Ennepe-Ruhr-Kreis, North Rhine-Westphalia in Germany. It is located south of Dortmund in the Ruhr Area. Its location between the two Ruhr reservoirs Hengsteysee and Harkortsee has earned it the nickname Die Stadt zwischen den Ruhrseen.

The Ennepe-Ruhr-Kreis is a district in the center of North Rhine-Westphalia, Germany. It is part of the southern Ruhr urban area and has ca. 324,000 inhabitants (2012). The district's seat is Schwelm; the largest of its nine towns is Witten.